This invention relates to a process for preparing 7-(1-hydroxyethyl)-3-(2-aminoethylthio)-1-carbadethiaceph-3-em-3-carboxyli c acid and its pharmaceutically acceptable salts and esters (I) which are useful as antibiotics: ##STR2## The compound of Structure I might for convenience be called "homothienamycin" on reference to the known antibiotic thienamycin III: ##STR3##
Homothienamycin (I) is disclosed and claimed in co-pending, commonly assigned U.S. patent application Ser. No. 903,455 (filed May 8, 1978) which is incorporated herein by reference to the extent that it describes I and its utility as an antibiotic. Also incorporated by reference is U.S. Pat. No. 3,950,357 which discloses and claims thienamycin; this patent is incorporated by reference to the extent that it teaches the utility of antibiotics such as III and by analogy I.
The process of the present invention is a total synthesis, starting with L-aspartic acid and proceeding in a stereo-selective manner via intermediates II and IIa (4-iodomethylazetidin-2-one): ##STR4## wherein R is a conventional protecting group. The details of the total synthesis are given below.